Was there a big warning sign on the graph saying
‘We have mixed up two different bits of data here to give a pleasing and iconic graph, but you should use this with extreme care because it is not telling you what a casual reader is likely to be misled into thinking it does. We know all about this likelihood but can’t be arsed to do it right. Caveat emptor’?
Because if it doesn’t, they weren’t explicit enough at the time.
Nor did they correct this misleading impression when the Hockey Stick became the ‘poster child’ for every green cause around the world before it was debunked and shown to be wrong.
The IPCC likes to think of itself as the Authoritative Reference on all matters climate related. With that power comes responsibility. The authors of the graph did not act responsibly in creating it, and the wider IPCC did not do so by allowing them that latitude.